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69 lines
2.3 KiB
Markdown
69 lines
2.3 KiB
Markdown
Disk: Northstar
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================
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Northstar Floppy disks use 10-sector hard sectored disks with either FM or MFM
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encoding. They may be single- or double-sided. Each of the 10 sectors contains
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256 (FM) or 512 (MFM) bytes of data. The disk has 35 cylinders, with tracks 0-
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34 on side 0, and tracks 35-69 on side 1. Tracks on side 1 are numbered "back-
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wards" in that track 35 corresponds to cylinder 34, side 1, and track 69
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corresponds to cylinder 0, side 1.
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The Northstar sector format does not include any head positioning information.
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As such, reads from Northstar floppies need to by synchronized with the index
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pulse, in order to properly identify the sector being read. This is handled
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automatically by FluxEngine.
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Due to the nature of the track ordering on side 1, an .nsi image reader and
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writer are provided for double-sided disks. The .nsi image writer supports
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both single- and double-sided disks; however single-sided .nsi images are
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equivalent to .img images.
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Reading disks
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-------------
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You must use a 48-TPI (40-track) 300RPM 5.25" floppy drive.
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To read a double-sided North Star floppy, run:
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```
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fluxengine read <format>
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```
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...where `<format>` is one of the formats listed below.
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You should end up with a `northstar.nsi` with a file size dependent on the floppy
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disk type.
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Writing disks
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-------------
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You must use a 48-TPI (40-track) 300RPM 5.25" floppy drive and make
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sure that the drive's spindle speed is adjusted to exactly 300RPM.
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To write a double-sided North Star floppy, run:
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```
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fluxengine write <format> -i image_to_write.nsi
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```
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...where `<format>` is one of the formats listed below.
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Available formats
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-----------------
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The following formats are supported:
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| Format name | Disk Type | File Size (bytes) |
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| -------------- | ----------------------------------- | ----------------- |
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| `northstar87` | Single-Sided, Single-Density (SSSD) | 89,600 |
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| `northstar175` | Single-Sided, Double-Density (SSDD) | 179,200 |
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| `northstar350` | Double-Sided, Double-Density (DSDD) | 358,400 |
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Useful references
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-----------------
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- [MICRO-DISK SYSTEM MDS-A-D DOUBLE DENSITY Manual][northstar_mds].
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Page 33 documents sector format for single- and double-density.
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[northstar_mds]: http://bitsavers.org/pdf/northstar/boards/Northstar_MDS-A-D_1978.pdf
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